1. Field of the Invention
The present invention relates to an organic semiconducting material including a naphthalocyanine derivative of a specific structure, a film containing such an organic semiconducting material, and organic electronic devices, especially an organic photoelectric transducer and an organic transistor, and an infrared dye composition which each use such an organic semiconducting material.
2. Description of the Related Art
Devices using organic semiconducting materials can be manufactured by simple processes as compared with traditional devices using inorganic semiconducting materials including silicon and the like. In addition, organic semiconducting materials can have their variations in plenty because their material characteristics can be altered easily by modification of their molecular structures. Therefore, it is conceivable that organic semiconducting materials will allow realization of such functions and devices as have never been achieved by inorganic semiconducting materials, and recent years have seen extensive studies of devices using organic semiconducting materials. Examples of a device using an organic semiconducting material include photoelectric transducers using organic semiconducting materials as photoelectric conversion materials, such as organic thin-film solar cells and solid-state image pickup devices, and organic transistors (Shinkasuru Yuki Handotai, NTS Inc. (2006)).
The use of organic semiconducting materials allowing film formation by a solution process makes it possible to manufacture large-area devices at low cost under low temperatures as compared with devices manufactured using inorganic semiconducting materials including silicon and the like. As an example of research on organic thin-film solar cells taking advantage of such a property, the case is proposed where the mixed film including a polythiophene derivative P3HT (poly(3-hexylthiophene)) and a fullerene derivative PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) is formed by a solution process and used as a photoelectric conversion layer. However, this case can not match silicon-utilized solar cells in photoelectric conversion capability, so further improvement in performance is required thereof. A cause of low energy conversion efficiency of organic thin-film solar cells consists in that the organic materials used therein show light absorption and photoelectric conversion in wavelength regions narrower than the wavelength region of the light radiating from the sun, and that they fail to utilize light in long wavelength region (infrared region) in particular (Kaku Uehara & Susumu Yoshikawa (editors), Yuki Hakumaku Taiyo Denchi no Saishin Gijutu (Leading-edge Technology for Thin Film Organic Photovoltaic Cells), pp. 1-8, CMC Publishing Co., Ltd. (2005)). Therefore, it is desired to develop organic photoelectric conversion materials which can be formed into film by use of a solution process and have sensitivity in the infrared region.
In the field of solid-state image pickup devices, on the other hand, a silicon-utilized image pickup device has low sensitivity in the infrared region and the inorganic semiconducting material used therein, such as silicon, absorbs all the light in the wavelength region shorter than the wavelength region corresponding to an energy quantity of the band gap. Therefore, it is impossible to subject only the infrared light to photoelectric conversion. By contrast, an organic semiconducting material allows photoelectric conversion of only the light in a specific wavelength region, and there is disclosure of the visible-light solid-state image pickup devices of multilayer structure which take advantage of such a property (JP-A-2003-234460, JP-A-2003-332551 and JP-A-2005-268609). If a photoelectric conversion film allowing photoelectric conversion of only the infrared light can be obtained as in the above cases, it is conceivable that sampling of visible light information and infrared light information at the same time and the same point becomes possible by laminating such a photoelectric conversion film and a visible-light solid-state image pickup device; as a result, a high-performance multifunctional device allowing image information synthesis and easy processing can be obtained. In uses of solid-state image pickup devices, requirements for device performance including an S/N ratio and so on are much higher than those for expansion of area and a low cost process. So, film formation by a vacuum process is preferable, because the film formed by vacuum process resists contamination with impurities and easily takes on a multilayer structure in combination with other functional films. Under these circumstances, it is also desired to develop organic photoelectric conversion materials which can be made into film by a vacuum process and have sensitivity to only infrared light.
Many of materials known as infrared dyes suffer decomposition by heating, and only limited number of infrared dyes can be formed into film by a vacuum process. As an example of infrared dyes allowing film formation by a vacuum process, though bistrihexylsiloxylsilicon naphthalocyanine is known, its intermolecular interaction in the solid film is too weak for using the compound as an organic semiconducting material, so further improvement in carrier transporting ability is required (Journal of the American Chemical Society, 106, 7404-7414 (1984) and JP-A-63-5093).